I was shooting my 6D today at the aviary. I believe I was in TV mode. Had my Canon 320EX speedlite on. I had been shooting with the flash off but turned it on. The shutter was set at 1/400th. The ISO was, I know, still set from the last room I was in, which was dark, so it is at ISO 3200.

Anyway, the camera failed to reduce the shutter to the camera's max sync speed (1/180) like you expect it to do. As a result, the flash was clearly out of sync with the shutter.

Also, the metadata says "flash did not fire". But obviously it did fire.

Could this be a firmware glitch? Bad camera? Some obvious user error I am overlooking?

Also, the metadata says "flash did not fire". But obviously it did fire.

Might really be like a broken camera shutter-sync or firmware problem, maybe Canon didn't test all combinations that extensively if they are very desperate to release the gear to counter the competition (In Germany this is called a "banana product", ripens when with the customer).

Maybe you should post this on the official US Canon forum, there are Canon mods around that might give you some mode inside advice, esp. if the problem is reproducible. When in doubt replace the camera body if it's easily done and still possible.

I don't think the camera is supposed to do this. Any time I'm using a flash I change things myself to fall under the limit, because if I manually set the shutter speed higher I know it's going to cause that issue. In manual mode or shutter-priority (TV), which are both modes where the user specifies the shutter speed, shouldn't the camera assume that because you're manually setting it at 1/400 that you're doing it on purpose?

@titokane: If you have selected a shutter speed higher than the max sync speed, the camera is supposed to override it when you turn the flash on. The instruction manual says so, and also I have seen Canon cameras do this many times.

@ Marsu: 1.) It was not in HSS, and 2.) I was wondering about whether the old flash was maybe not included in the 6d's firmware as you say, and 3.) I actually did post this simultaneously on the official Canon forum just as you also thought. So far I have one response suggesting that maybe I didn't have the flash seated fully forward in the flash mount, and Canon's moderator gave that poster a "KUDOS" for the suggestion, but did not offer any insights from Lake Success.

@ScottyP Can you show me in the manual where you're talking about? I see a reference to something like that when using Av mode (manual page 173, "Flash Synchronization Speed in Av Mode"), but nothing where the user is manually setting the shutter, like in Tv mode. Generally I think it would drive me nuts if the camera was automatically overriding my manual settings. If the user is in Aperture Priority mode, the camera can make all the decisions about shutter it wants, especially limiting it to the sync speed. In Shutter Priority, the user should be making all shutter decisions, for better or for worse, no matter what the camera thinks is correct.

@titokane , I was already pretty sure that the camera would always override shutter, but just in case you were right I just tested on an EOS 50e and t4i . In Tv mode they are both limited to 1/200 and slower with the flash enabled. The fact that EXIF says the flash did not fire should tell you something is not working... if it did recognize the flash it would limit the shutter to 1/180.

Update: I actually checked how well the flash was mounted, and to my surprise, although the tightening lever was deployed and everything, the speedlite WAS slid back in the hotshoe mount, and by quite a lot.

I pushed it back forward like it is supposed to be and suddenly the camera is doing what it should. I set it in TV and selected 1/640th shutter. Took a few underexposed test-shots, and then turned on the speedlite. BANG. The camera overrode my shutter setting and reduced my shutter speed to 1/180th. It worked 3 times, so I am calling this SOLVED.

I feel a little silly, but that is still way better than if there were a major problem with the camera.

On the other hand, I wonder if you could "squeek" a little higher sync speed out of the camera (just 1/250th maybe) by deliberately mis-mounting the flash in the hotshoe.

Update: I actually checked how well the flash was mounted, and to my surprise, although the tightening lever was deployed and everything, the speedlite WAS slid back in the hotshoe mount, and by quite a lot.

I pushed it back forward like it is supposed to be and suddenly the camera is doing what it should. I set it in TV and selected 1/640th shutter. Took a few underexposed test-shots, and then turned on the speedlite. BANG. The camera overrode my shutter setting and reduced my shutter speed to 1/180th. It worked 3 times, so I am calling this SOLVED.

I feel a little silly, but that is still way better than if there were a major problem with the camera.

On the other hand, I wonder if you could "squeek" a little higher sync speed out of the camera (just 1/250th maybe) by deliberately mis-mounting the flash in the hotshoe.

I feel a little silly, but that is still way better than if there were a major problem with the camera.

As long as you're only feeling just a *little* silly :-> ... actually my first guess was that the flash wasn't mounted correctly, but then I didn't write it because I thought you'd surely have checked it and when tightening the 430ex2/600rt-type flashes they have to be mounted correctly :-o

On the other hand, I wonder if you could "squeek" a little higher sync speed out of the camera (just 1/250th maybe) by deliberately mis-mounting the flash in the hotshoe.

As far as I understand x-sync that isn't possible since 1/180s (on the 6d) is the max. shutter when the first curtain is down and the second curtain is still up, so there is a brief moment with full sensor exposure. On faster speeds the second curtain goes down sooner leaving only a slit that moves across the sensor.